Circumference of a Circle
Also known as 2πr · distance around a circle
Enter your known values, leave one input blank, and solves for the missing one. Try different units for next level excitement!
Learning zone
Circumference is where π was born: the ratio of any circle's perimeter to its diameter is always the same number, 3.14159… A useful field trick — wrap a tape around a pipe, divide by π, and you have its outside diameter.
Circumference of a Circle
Where
- = Circumference
- = Radius
Missing one of these? Work it out first, then come back
- Circumference — Pythagorean Theorem, Area of a Circle
- Radius — Area of a Circle, Circular Sector Area